Peptide YY administration into the posterior hypothalamic nucleus of the rat evokes cardiovascular changes by non-adrenergic, non-cholinergic mechanisms.

Abstract

1 Microinjection of peptide YY (PYY) (0.23-2.3 nmol) into the posterior hypothalamic nucleus (PHN) of conscious rats evokes a dose-dependent pressor response and a bradycardia. 2 The increase in mean arterial pressure evoked by 2.3 nmol of PYY was not blocked by intravenous pretreatment with: (i) the nicotinic ganglionic receptor antagonist pentolinium (PENT, 10 mg kg(-1)) alone, or in combination with the muscarinic receptor antagonist methylatropine (MeATR, 1 mg kg(-1)); (ii) the alpha(1)-adrenoceptor antagonist prazosin (PRAZ, 0.2 mg kg(-1)); (iii) the V(1)-vasopressin receptor antagonist [d(CH(2))(5)Tyr(Me)]AVP (AVPX, 20 microg kg(-1)); (iv) the combination of AVPX, PENT and MeATR; (v) the combination of PRAZ, AVPX, PENT, MeATR, and the alpha(2)-adrenoceptor antagonist yohimbine (0.3 mg kg(-1)); or (vi) the angiotensin II type 1 receptor antagonist ZD 7155 (1 mg kg(-1)). 3 Adrenal demedullation inhibited the PYY-evoked responses of drug-naive rats, and rats pretreated with the combination of PENT, MeATR and AVPX. 4 Transection of the splanchnic nerve innervating the adrenal medullae attenuated the bradycardia, as did ZD 7155, but not the PYY-evoked pressor response. 5 Systemic pretreatment of rats with the neuropeptide Y(1) receptor antagonist BIBP 3226 (1 mg kg(-1)) blocked the PYY-evoked cardiovascular changes, but not those evoked by microinjection of carbachol (5.5 nmol) into the PHN. 6 These results suggest that the cardiovascular changes evoked from the PHN by PYY requires the presence of the adrenal medullae, which are stimulated by: (i) a hormone to release an NPY-like substance that evokes the pressor response, and (ii) the splanchnic nerve to evoke the release of a substance that results in the bradycardia.

• Authors: J R Martin
• Journal: Autonomic & autacoid pharmacology (Auton Autacoid Pharmacol) Vol. 25 Issue 2 Pg. 53-67 (Apr 2005) ISSN: 1474-8665 [Print] England
• PMID: 15757505 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Parasympatholytics
• Parasympathomimetics
• Peptide YY

Topics

• Adrenal Glands (innervation, physiology)
• Animals
• Autonomic Nervous System (physiology)
• Blood Pressure (drug effects)
• Denervation
• Dose-Response Relationship, Drug
• Heart Rate (drug effects)
• Hemodynamics (drug effects)
• Hypothalamus, Posterior (physiology)
• Microinjections
• Parasympatholytics (administration & dosage, pharmacology)
• Parasympathomimetics (administration & dosage, pharmacology)
• Peptide YY (administration & dosage, pharmacology)
• Rats
• Rats, Sprague-Dawley
• Splanchnic Nerves (physiology)
• Stereotaxic Techniques